No Evidence for Enhancing Prospective Memory with Anodal Transcranial Direct Current Stimulation across Dorsolateral Prefrontal Cortex

A standard finding in the event-based prospective memory literature is that focal cues are more often detected than nonfocal cues. The multiprocess view of prospective memory accounts for this result by suggesting that dorsolateral prefrontal cortex (DLPFC) mediated executive processes are necessary for nonfocal cue detection while hippocampally mediated spontaneous retrieval processes support detection of focal cues. In agreement with the multiprocess view, previous studies have found that working memory capacity is predictive of prospective memory performance through detection of nonfocal cues, but non-predictive for focal cues. Because the DLPFC is known to support working memory maintenance, we predicted that anodal transcranial direct current stimulation (tDCS) of the DLPFC would increase prospective memory cue detection for nonfocal cues when compared with a sham condition. Critically, we also expected an interaction between prospective memory cue type and stimulation such that anodal stimulation would not influence focal cue detection. Our results replicated the standard effect of improved focal compared to nonfocal cue detection. However, there was no significant effect between the sham and active tDCS conditions. Furthermore, we did not find the expected interaction between cue type and stimulation. Not only do our findings add onto the growing literature of tDCS experiments that failed to find stimulation effects to DLPFC, but it is also one of the first studies to incorporate prospective memory with tDCS.